Optical fibers have acquired an increasingly important role in field of communications, frequently replacing existing copper wires. This trend has a significant impact in local area networks (i.e., for fiber-to-home uses), which has seen a vast increase in the usage of optical fibers. Further increases in the use of optical fibers in local loop telephone and cable TV service are expected, as local fiber networks are established to deliver ever greater volumes of information in the form of data, audio, and video signals to residential and commercial users. In addition, use of optical fibers in home and commercial business environments for internal data, voice, and video communications is expected to increase.
Optical fibers are often bundled together to form a product known as an optical fiber ribbon. The ribbon includes optical fibers that have been encased or encapsulated in a polymeric matrix material to secure the fibers in a parallel arrangement. The matrix portion of the optical fiber ribbon can include one or more layers of the polymeric matrix material, and each optical fiber typically contains a dual layer coating system that includes a soft, inner polymer coating and a hard, protective outer polymer coating. Prior to forming the ribbon, the optical fibers may also be coated with a thin colored layer of marking ink (i.e., in a polymer base) for purposes of fiber identification within the ribbon.
While the most basic function of the matrix materials is to secure the individual optical fibers or ribbon sub-units in a planar array, they also contribute to the handling properties of the ribbon. Two important handling attributes of the optical fiber ribbon are peel and breakout performance. Peel is the removal of matrix material from the optical fibers in the mid-span region of the optical fiber ribbon. It is desirable, for example, to be able to peel the matrix layers cleanly off the optical fibers without removing any of the colored marking ink layers. In addition, the matrix layers should be removable as an intact unit without breaking apart and leaving residue on the optical fibers. Breakout occurs at the ends of the ribbons and is used to provide access to individual fibers in the ribbon. As with peel, it is desirable to be able to remove the matrix material during breakout without it breaking apart and leaving residue on the optical fibers.
In general, the matrix material must be tough enough such that the matrix does not easily break apart during breakout and peel. Greer (U.S. Pat. No. 6,334,016) teaches that the matrix material must exhibit sufficient toughness such that the matrix material does not easily break apart when removed from the optical fiber ribbon. Greer further teaches that the matrix materials typically comprise an acrylated urethane oligomer. This is because the hydrogen bonding associated with the urethane linkages contributes to enhanced toughness. Shustack (U.S. Pat. No. 6,455,607) also describes matrix materials having acrylated urethane oligomers. However, urethane acrylate oligomers are high cost components in UV-curable acrylate formulations. The cost savings associated with reducing or eliminating oligomer use in matrix formulations is desirable, however the resultant matrix material must maintain good breakout, peel, and other performance characteristics required of ribbon matrix materials.